A program that uses this library provides a simple emacs-like editing interface to its users. A line may be edited before it is sent to the calling program by typing either control characters or escape sequences. A control character, shown as a caret followed by a letter, is typed by holding down the ``control'' key while the letter is typed. For example, ``^A'' is a control-A. An escape sequence is entered by typing the ``escape'' key followed by one or more characters. The escape key is abbreviated as ``ESC''. Note that unlike control keys, case matters in escape sequences; ``ESC F'' is not the same as ``ESC f''.

An editing command may be typed anywhere on the line, not just at the beginning. In addition, a return may also be typed anywhere on the line, not just at the end.

Most editing commands may be given a repeat count, n, where n is a number. To enter a repeat count, type the escape key, the number, and then the command to execute. For example, ``ESC 4 ^f'' moves forward four characters. If a command may be given a repeat count then the text ``[n]'' is given at the end of its description.

The following control characters are accepted:

^A	Move to the beginning of the line
^B	Move left (backwards) [n]
^D	Delete character [n]
^E	Move to end of line
^F	Move right (forwards) [n]
^G	Ring the bell
^H	Delete character before cursor (backspace key) [n]
^I	Complete filename (tab key); see below
^J	Done with line (return key)
^K	Kill to end of line (or column [n])
^L	Redisplay line
^M	Done with line (alternate return key)
^N	Get next line from history [n]
^P	Get previous line from history [n]
^R	Search backward (forward if [n]) through history for text;
	prefixing the string with a caret (^) forces it to
	match only at the beginning of a history line
^T	Transpose characters
^V	Insert next character, even if it is an edit command
^W	Wipe to the mark
^X^X	Exchange current location and mark
^Y	Yank back last killed text
^[	Start an escape sequence (escape key)
^]c	Move forward to next character ``c''
^?	Delete character before cursor (delete key) [n]

The following escape sequences are provided.

ESC ^H	Delete previous word (backspace key) [n]
ESC DEL	Delete previous word (delete key) [n]
ESC ESC	Show possible completions; see below
ESC SP	Set the mark (space key); see ^X^X and ^Y above
ESC .	Get the last (or [n]'th) word from previous line
ESC ?	Show possible completions; see below
ESC <	Move to start of history
ESC >	Move to end of history
ESC b	Move backward a word [n]
ESC d	Delete word under cursor [n]
ESC f	Move forward a word [n]
ESC l	Make word lowercase [n]
ESC m	Toggle if 8bit chars display as themselves or with
	an ``M-'' prefix
ESC u	Make word uppercase [n]
ESC y	Yank back last killed text
ESC w	Make area up to mark yankable
ESC nn	Set repeat count to the number nn
ESC C	Read from environment variable ``_C_'', where C is
	an uppercase letter

The editline library has a small macro facility. If you type the escape key followed by an uppercase letter, C, then the contents of the environment variable _C_ are read in as if you had typed them at the keyboard. For example, if the variable _L_ contains the following: ^A^Kecho '^V^[[H^V^[[2J'^M Then typing ``ESC L'' will move to the beginning of the line, kill the entire line, enter the echo command needed to clear the terminal (if your terminal is like a VT-100), and send the line back to the shell.

The editline library also does filename completion. Suppose the root directory has the following files in it:

bin	vmunix
core	vmunix.old

If you type ``rm /v'' and then the tab key. Editline will then finish off as much of the name as possible by adding ``munix''. Because the name is not unique, it will then beep. If you type the escape key followed by either a question mark or another escape, it will display the two choices. If you then type a period and a tab, the library will finish off the filename for you:

rm /v[TAB]munix.[TAB]old

The tab key is shown by ``[TAB]'' and the automatically-entered text is shown in italics.